Clinical inquiries. Should the varicella vaccine be given to all children to prevent chickenpox?

In a search of the literature from 1966 to 2000, a systematic review identified 24 randomized controlled trials and 18 cohort studies of varicella vaccination. (3) In children aged 10 months to 14 years, 1 randomized controlled trial found protective efficacy of 100% over 9 months and 98% over 7 years. (4) A second trial showed efficacy of 72% over 29 months. (5) Cohort studies of children report that the vaccine is 84% to 86% effective in preventing varicella and 100% effective in preventing moderate to severe infections. (3)